The present invention relates to a method for continuously and stably winding a rapidly quenched thin metal ribbon, an apparatus for producing a rapidly quenched thin metal ribbon, and a coil of a rapidly quenched thin metal ribbon produced by using the above method.
A rapid quenching method of a molten metal is widely known for the production of thin metal ribbons. The rapid quenching method includes, for example, a single-roll method comprising ejecting a molten metal onto a cooling roll rotating at a high speed to rapidly solidify the molten metal to obtain a thin metal ribbon, and a twin-roll method comprising feeding a molten metal between a pair of cooling rolls rotating at a high speed to produce a thin metal ribbon. To continuously wind the thin metal ribbon produced by these methods, various methods have been proposed heretofore. For example, Japanese Patent Laid-Open No. 57-94453 discloses a method comprising rapidly solidifying a thin metal ribbon on a cooling roll, peeling the rapidly solidified thin metal ribbon from the cooling roll using a high-pressure gas jet, and allowing a winding roll having a permanent magnet such as a permanent SmCo magnet embedded in a surface rotating at about the same surface speed as the cooling roll to magnetically attract the front end portion of the peeled thin metal ribbon, thereby continuously winding the thin metal ribbon.
Japanese Patent Laid-Open No. 8-318352 proposes a method using winding roll having an electromagnet embedded in a surface, the electromagnet being actuated at the start of winding to attract the font end of a thin metal ribbon. In each of these methods, a thin metal ribbon is continuously wound while a winding roll rotates. However, each method is disadvantageous, for example, in that the winding roll has a complex structure requiring troublesome maintenance.
Besides, there is proposed a method of winding a thin metal ribbon not from its front end portion but from its intermediate portion. As such a method, Japanese Patent Laid-Open No. 2-55647 proposes a method comprising leading a thin metal ribbon to an additional course with a guide, cutting the thin metal ribbon with a cutter, and then returning the cut thin metal ribbon to a regular course for winding.
Though the method of Japanese Patent Laid-Open No. 2-55647 is effective in that an undesirable forward excess portion of the thin metal ribbon is cut away, a very high skill is needed to lead a thin metal ribbon by a guide and cut it by a cutter in the case of a thin metal ribbon produced by high-speed casting.
In general, because the front end portion of a thin metal ribbon supplied from a cooling roll unstably moves, it is very difficult to lead the front end portion of the thin metal ribbon to an intended course in which a winding roll is positioned.
Accordingly, an object of the present invention is to provide a method for winding a rapidly quenched thin metal ribbon continuously and stably using an apparatus of simple structure and easy maintenance, an apparatus for winding a rapidly quenched thin metal ribbon, and a rapidly quenched thin metal ribbon coil.
In view of the above object, the inventors have found that a thin metal ribbon supplied from a cooling roll would easily be wound, if the thin metal ribbon were let to freely move from the cooling roll, and if winding were started by bringing a winding roll having an adhesive on a surface into contact with the freely moving thin metal ribbon at an intermediate point thereof after the free movement of the thin metal ribbon has become stabile. The present invention has been completed based on this finding.
The present invention provides a method for winding a rapidly quenched thin metal ribbon, comprising the steps of (1) ejecting a molten metal onto a rotating cooling roll to rapidly solidify the molten metal to form a thin metal ribbon, (2) peeling the thin metal ribbon from the cooling roll to let the thin metal ribbon to freely move from the cooling roll, and (3) bringing a rotating winding roll having an adhesive thereon into contact with the freely moving thin metal ribbon at an intermediate point thereof, so that the thin metal ribbon is wound around the winding roll with an excess portion of the thin metal ribbon forward of the intermediate point cut off.
The present invention also provides an apparatus for producing a rapidly quenched thin metal ribbon, comprising a crucible for containing a molten metal; a feeder equipped with a nozzle for ejecting the molten metal; a rotary cooling roll for rapidly solidifying the molten metal ejected from the nozzle on a surface thereof to form a thin metal ribbon; and a rotary winding roll having an adhesive thereon, wherein the winding roll is brought into contact with the freely moving thin metal ribbon at an intermediate point thereof, so that the thin metal ribbon is wound around the winding roll with an excess portion of the thin metal ribbon forward of the intermediate point cut off.
In the apparatus of the present invention, the winding roll is preferably movable toward and away from a free movement course of the thin metal ribbon, the winding roll being positioned away from the free movement course of the thin metal ribbon until the free movement of the thin metal ribbon becomes stable, and the winding roll being moved to a position at which it is brought into contact with the freely moving thin metal ribbon after the free movement of the thin metal ribbon becomes stable.
Upon brought into contact with the winding roll having an adhesive on a surface, the freely moving thin metal ribbon is suddenly pulled in a rotational direction of the winding roll, different from the free movement direction, whereby the thin metal ribbon is broken substantially at a contact point, leaving an excess portion of the thin metal ribbon forward of the contact position cut off. To ensure that the thin metal ribbon is broken substantially at a point of contact with the winding roll having an adhesive on a surface, the surface speed of the winding roll is preferably 0.1 to 2.0% higher than the surface speed of the cooling roll.
The present invention further provides a rapidly quenched thin metal ribbon coil wound around a winding roll having an adhesive thereon, wherein an end of the thin metal ribbon, from which the thin metal ribbon starts to be wound around the winding roll, is a cut end, with a forward excess portion of the thin metal ribbon cut off.